title: Coordinated transporter activity shapes high-affinity iron acquisition in cyanobacteria.
abstract: Iron bioavailability limits biological activity in many aquatic and terrestrial environments. Broad scale genomic meta-analyses indicated that within a single organism, multiple iron transporters may contribute to iron acquisition. Here, we present a functional characterization of a cyanobacterial iron transport pathway that utilizes concerted transporter activities. Cyanobacteria are significant contributors to global primary productivity with high iron demands. Certain cyanobacterial species employ a siderophore-mediated uptake strategy; however, many strains possess neither siderophore biosynthesis nor siderophore transport genes. The unicellular, planktonic, freshwater cyanobacterium, Synechocystis sp. PCC 6803, employs an alternative to siderophore-based uptake-reduction of Fe(III) species before transport through the plasma membrane. In this study, we combine short-term radioactive iron uptake and reduction assays with a range of disruption mutants to generate a working model for iron reduction and uptake in Synechocystis sp. PCC 6803. We found that the Fe(II) transporter, FeoB, is the major iron transporter in this organism. In addition, we uncovered a link between a respiratory terminal oxidase (Alternate Respiratory Terminal Oxidase) and iron reduction - suggesting a coupling between these two electron transfer reactions. Furthermore, quantitative RNA transcript analysis identified a function for subunits of the Fe(III) transporter, FutABC, in modulating reductive iron uptake. Collectively, our results provide a molecular basis for a tightly coordinated, high-affinity iron transport system.
authors.affiliation: 1] Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel [2] Interuniversity Institute for Marine Sciences in Eilat, Eilat, Israel.
authors.forename: Chana
authors.initials: C
authors.lastname: Kranzler
authors.affiliation: 1] Interuniversity Institute for Marine Sciences in Eilat, Eilat, Israel [2] The Freddy and Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Hagar
authors.initials: H
authors.lastname: Lis
authors.affiliation: Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Omri M
authors.initials: OM
authors.lastname: Finkel
authors.affiliation: Institute of Physical Chemistry, University of Vienna, Vienna, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Schmetterer
authors.affiliation: 1] Interuniversity Institute for Marine Sciences in Eilat, Eilat, Israel [2] The Freddy and Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Yeala
authors.initials: Y
authors.lastname: Shaked
authors.affiliation: Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Nir
authors.initials: N
authors.lastname: Keren
mesh_terms: D001692:Biological Transport / Q000235:genetics; D005290:Ferric Compounds / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation; D046939:Synechocystis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D026901:Membrane Transport Proteins; D007501:Iron